1. Field of the Invention
The present invention relates generally to a tether assembly for a fiber optic communications network and, more particularly, to a tether assembly including a first end adapted for interconnection with a fiber optic distribution cable and a second end terminating in one or more individual connector ports, wherein each connector port provides access to at least one optical fiber interconnected with at least one optical fiber of the distribution cable.
2. Description of the Related Art
Optical fiber is increasingly being used for a variety of broadband communications including voice, video and data transmissions. As a result of the ever increasing demand for broadband communications, fiber optic networks typically include a large number of mid-span access locations at which one or more optical fibers are terminated from a distribution cable and interconnected with another fiber optic cable, such as a branch cable or a drop cable. The mid-span access locations provide an interconnection point, also referred to herein as a “tap” point, from the distribution cable leading to a network distribution terminal, or from the distribution cable leading directly to an end user, commonly referred to as a subscriber, thereby extending an “all optical” communications network closer to the subscriber. In this regard, fiber optic networks are being developed that deliver “fiber-to-the-curb” (FTTC), “fiber-to-the-business” (FTTB), “fiber-to-the-home” (FTTH), or “fiber-to-the-premises” (FTTP), referred to generically as “FTTx.”
In one example of a fiber optic communications network, one or more drop cables are interconnected with a distribution cable at a mid-span access location. Substantial expertise and experience are required to configure the optical connections in the field. In particular, it is often difficult to identify a particular optical fiber of the distribution cable to be optically connected with an optical fiber of a drop cable. Once identified, the optical fiber of the distribution cable is typically joined directly to the optical fiber of the drop cable at the mid-span access location using conventional splicing techniques, such as fusion splicing. In other instances, the optical fiber of the distribution cable and the optical fiber of the drop cable are each first spliced to a short length of optical fiber having an optical connector mounted on the other end, which is generally referred to in the art as a “pigtail.” The pigtails are then routed to opposite sides of an adapter or connector alignment sleeve to align and interconnect the drop cable with the distribution cable. In either case, the process of configuring the mid-span access location is not only time consuming, but frequently must be accomplished by a highly skilled field technician at significant cost and under field working conditions that are less than ideal. In situations in which a mid-span access location is enclosed within a conventional splice closure, reconfiguring optical connections within the splice closure is especially difficult, based in part on the relatively inaccessible location of the closure, the limited workspace available within the closure, and the inability to readily remove the closure from the distribution cable. Further, once the optical connections are spliced, it is labor intensive, and therefore relatively costly, to reconfigure the optical connections or to add additional optical connections.
In order to reduce installation costs by permitting less experienced and less skilled technicians to make optical connections and to reconfigure optical connections at mid-span access locations in the field, communications service providers are increasingly pre-engineering new fiber optic networks and demanding factory-prepared interconnection solutions, commonly referred to as “plug-and-play” type systems. There are currently several methods to build a distribution cable assembly for economical deployment and field installation. In one example, the distances between desired network interconnection locations (i.e., tap points) are measured with great accuracy and a distribution cable is assembled in the factory with mid-span access locations positioned precisely at the desired tap points. However, in this instance the length of the distribution cable between mid-span access locations must be exact, and the deployment of the distribution cable must be performed accurately so that each tap point is positioned at the predetermined location. If the length of the span of distribution cable between adjacent mid-span access locations is short, or if the position of even one tap point is incorrect, the error could have a compounding effect on the position of each downstream mid-span access location. As a result, all downstream mid-span access locations will be positioned upstream of their intended location and the distribution cable will not extend to the end of the cable run.
Obviously, measuring the required distances between mid-span access locations and assembling a distribution cable with accurate distances between mid-span access locations is a difficult undertaking. Furthermore, an error in the manufacturing process may result in the entire distribution cable assembly being unusable, and therefore scrapped. Alternatively, an excess length of cable (i.e., cable slack) may be intentionally built into the distribution cable at each mid-span access location to insure that the tap point can always be positioned in the field at precisely the predetermined location. The obvious drawbacks with such a distribution cable assembly are the cost associated with the excess lengths of the cable and the associated need to store the cable slack in a practical yet aesthetic manner.
In addition to the difficulties associated with manufacturing a distribution cable assembly having the mid-span access locations in the pre-engineered locations, there are also problems encountered with using conventional components to optically connect the optical fibers of the distribution cable with optical fibers of a branch cable or drop cable at the tap points. For example, rigid enclosures are typically used to protect the section of the distribution cable that must be exposed to access the appropriate optical fibers and to house the spliced optical connections. Distribution cables provided with conventional enclosures tend to be large in size and relatively inflexible. As a result, the distribution cable is unable to satisfy common shipping and deployment constraints, such as being wound onto a reel and deployed through conduits having a relatively small inner diameter or significant bends, or deployed through conventional aerial lashing equipment, such as sheaves and rollers. Furthermore, such enclosures are often structurally complex and difficult to install.
Several alternatives have been proposed to overcome the disadvantages of rigid enclosures, while at the same time providing a practical solution for mitigating span length differences that arise as a result of a span length measurement, cable manufacturing or cable deployment error. In one alternative, a tether assembly adapted for interconnection with a distribution cable includes a tether cable terminating in a relatively flexile optical connection terminal having one or more connector ports. Each connector port typically includes a receptacle for readily connecting an optical fiber of a connectorized fiber optic branch cable or drop cable to an optical fiber of the distribution cable. Although a tether assembly including an optical connection terminal provides convenient access to the terminated optical fibers of the distribution cable and mitigates span length differences, several disadvantages remain. For instance, while the optical connection terminal is generally smaller than a conventional field-installed enclosure, installation limitations may still exist based on the size and profile of the terminal. This is particularly so when a large number of optical fibers must be terminated at a mid-span access location, thus requiring an optical connection terminal having a greater number of connector ports, such as eight or twelve. In addition, a unitary optical connection terminal does not allow access to a particular connector port without disturbing the remaining connector ports and any previous optical connections. This is particularly important in a vault, hand-hole or pedestal installation where it would be convenient and advantageous to access a particular connector port without having to remove the entire optical connection terminal from the enclosure or to reposition the terminal within the enclosure to access the desired connector port. Because of the location of the optical connection terminal or the number of drop cables previously connected to other connector ports, it may be difficult to remove or reposition the terminal within the enclosure. Still further, a unitary optical connection terminal is typically more difficult to seal because of the size and shape needed to accommodate a plurality of connector ports.
Accordingly, there is a specific and unresolved need for a tether assembly adapted for interconnection with a distribution cable in a fiber optic communications network that overcomes the specific disadvantages described above. For example, a tether assembly is needed that provides convenient and ready access to the terminated optical fibers of the distribution cable, while mitigating any difference between a pre-engineered span length measurement and the actual span length following deployment of the distribution cable that may arise as a result of a network measurement, cable assembly manufacturing, or cable deployment error. What is also needed is a factory-prepared tether assembly having a plurality of connector ports that provides access to an individual connector port without disturbing the remaining connector ports. In a particular embodiment, a factory-prepared fiber optic distribution cable preferably includes a tether assembly having an upstream end adapted for connection to terminated optical fibers of the distribution cable and a downstream end terminating in a plurality of individual connector ports, wherein each connector port provides access to at least one optical fiber interconnected with at least one of the terminated optical fibers of the distribution cable. Such a fiber optic distribution cable assembly would not require a highly-skilled field technician or extensive field labor to interconnect an optical fiber of the distribution cable with an optical fiber of a branch cable or drop cable at a tap point in a pre-engineered fiber optic communications network.